In inspection or measurement of a structure using ultrasonic waves, in a case in which a material having a coarse crystal grain diameter in which a molten metal is crystallized, or a material having an acoustic anisotropy by growing the crystal grains of the metal along a certain direction is used as a target, it is known that material properties greatly affect a result of the inspection or measurement. The material of the coarse crystal grains is strongly affected by scattering due to a wavelength of an ultrasonic wave, so that an ultrasonic transmission property is deteriorated. Therefore, the wavelength of the ultrasonic wave, which is sufficiently longer than an average grain diameter and is unlikely to be scattered with the crystal grains, is required to be used. In the material having acoustic anisotropy, for example, in a case in which the ultrasonic inspection image is output by isotropic-approximating, a sound velocity depending on a propagation direction cannot be correctly reflected to an inspection image, and thus there is a problem in that position accuracy, or the like is deteriorated. Therefore, it is necessary that the sound velocity depending on a direction where the ultrasonic wave is propagated is calculated and the ultrasonic inspection image is output.
As a member having a great effect on material properties due to such crystallinity being included, a unidirectional solidification material, a metal welding portion, or the like is exemplified. The unidirectional solidification material is made of thin and long crystal grains (columnar crystals), and crystal structures of each of the columnar crystals are the same as each other. Each of the columnar crystals at the time of solidification is aligned toward substantially in a crystal growth direction. However, crystal orientation of each of the columnar crystals in a plane perpendicular to this direction is random. Therefore, if the crystal orientations of all of the columnar crystals are averaged, the material is a material in which the crystal orientation is substantially along only a crystal axis of a longitudinal direction of the crystal grains. In the metal welding portion, the metal is crystallized in a procedure of melting and solidification of the metal, the metal welding portion has a relatively large crystal grain diameter, and there is a tendency that the crystals are grown in a vertical direction when being closer to the center of the welding portion. Therefore, locally, the metal welding portion seems to be a unidirectional solidification material; however, entirely, the metal welding portion is a solidification formation having a different crystal growth direction. Further, a structure including the welding portion is a structure which is divided into a region having the acoustic anisotropy and a region of an acoustic isotropy, when considering that an acoustic isotropic general metal where a sound velocity is not dependent on a propagation direction is bonded. Accordingly, improving of reliability of an output result is important by performing inspection or measurement under consideration of crystal states of the acoustic anisotropy region, or the acoustic isotropy region, and the anisotropy region.
These are known as materials or members which are relatively difficult to inspect or measure using the ultrasonic wave, and elucidation of an ultrasonic propagation phenomenon by numeral analysis is actively carried out. In order to output a simulation result having high reliability, it is important that an accurate model is created under consideration of a crystal state of a structure (distribution of crystal grain or crystal orientation of each crystal grain).
In PTL 1, it is disclosed that the welding portion is divided into a plurality of large regions, and a model including information of a crystal structure and a crystal growth direction is created in every region. A method of generating a model having high accuracy is disclosed, using the created model, and correcting the welding portion model so that a difference between a calculation flaw detection signal, which is an ultrasonic flaw detection signal calculated by a simulation, and the actually measured ultrasonic flaw detection signal is reduced.